Conventional surface protective layers and interlayer insulating layers for semiconductor devices typically include a polyimide resin that can have excellent heat resistance, electrical properties, mechanical properties, and the like. The polyimide resin has recently been used as a photosensitive polyimide precursor composition which can be coated easily. The photosensitive polyimide precursor composition can be coated on a semiconductor device, patterned by ultraviolet (UV) rays, developed, and thermally imidized, to easily provide a surface protective layer, an interlayer insulating layer, and the like. The use of a photosensitive polyimide precursor may remarkably shorten processing times as compared with a conventional non-photosensitive polyimide precursor composition.
The photosensitive polyimide precursor composition can be a positive type in which an exposed part is dissolved by development or a negative type in which the exposed part is cured and maintained. Positive type compositions may be developed using a non-toxic alkali aqueous solution.
The positive photosensitive polyimide precursor composition can include a polyimide precursor of polyamic acid, a photosensitive material of diazonaphthoquinone, and the like. However, it can be difficult to obtain a desired pattern using the positive photosensitive polyimide precursor composition because the carboxylic acid of the polyamic acid can be too highly soluble in an alkali.
In order to solve this problem, Japanese Patent Laid-Open Publication No. 10-307393 discusses a material including phenolic hydroxyl acid instead of a carbonic acid provided by esterifying polyamic acid with an alcohol compound having at least one hydroxyl group. This composition, however, may be insufficiently developed and thus may result in layer loss or resin delamination from a substrate.
Recently, a material prepared by mixing a polybenzoxazole precursor with a diazonaphthoquinone compound (see for example Japanese Patent Laid-Open Publication No. 1994-060140) has drawn attention. When the polybenzoxazole precursor composition is actually used, however, film loss of an unexposed part can be significantly increased, so it can be difficult to obtain a desirable pattern after the developing process.
In order to improve this, if the molecular weight of the polybenzoxazole precursor is increased, the amount of film loss of the unexposed part can be reduced. Development residue (scum), however, can be generated, so resolution may be decreased and the development duration on the exposed part may be increased.
In order to solve this problem, film loss can be suppressed in unexposed parts during development by adding a certain phenol compound to a polybenzoxazole precursor. See, for example Japanese Patent Laid-Open Publication No. 9-302221 and Japanese Patent Laid-Open Publication No. 2000-292913. However, the effect of suppressing the film loss of the unexposed part is insufficient. Accordingly, there is still a need to increase the effects on suppressing the film loss, along with preventing generation of the development residue (scum). In addition, there is still a need for research directed to a dissolution-suppressing agent, since phenol compounds used to adjust or control solubility can decompose at high temperatures during curing, can undergo a side reaction, or the like, which can damage mechanical properties of a cured film.
The positive photosensitive resin composition including the polybenzoxazole precursor may be used as an organic insulator or a barrier rib material in a display device field. A liquid crystal display device, which is one kind of a display device, can have the advantages of being light and thin, inexpensive, being operated with a small consumption of electricity, having excellent junction with an integrated circuit, and the like and thus, has been widely used for various electronic devices such as laptop computers, monitors, and TV images. This liquid crystal display device can include a lower substrate having a black matrix, a color filter, an ITO pixel electrode, and an upper substrate having an active circuit portion including a liquid crystal layer, a thin film transistor, a capacitor layer, and an ITO pixel electrode. The color filter can be fabricated by sequentially laminating a black matrix layer with a predetermined pattern on a transparent substrate to block light at pixel boundaries and pixel parts including a plurality of colors, in general, three primary colors of red (R), green (G), and blue (B).
In addition, an organic light emitting diode (OLED) actively developed in recent times is arranged as a pixel with a matrix format. These pixels are arranged to emit the same color to fabricate a single color display or as three primary colors of red (R), green (G), and blue (B) to display various colors.
Many attempts have been recently made to develop a display device having high contrast ratio and high luminance. One of the attempts forms a black filter layer between color patterns but this may not provide a high aperture ratio and can lower heat resistance and insulating properties. Another attempt to provide a high aperture ratio includes making a non-light emitting region black and simultaneously improving contrast ratio and visibility but this can deteriorate the inherent properties of an insulation layer because a large amount of colorant is dissolved and used. In addition, while an inorganic pigment such as carbon black and the like used for a black mill-base (a colorant) generally can have excellent light shielding properties, it can also deteriorate insulating resistance properties, which is not desirable in an insulation layer for an organic light emitting diode.
In contrast, an organic pigment consisting of a pigment mixture may provide a black color and thus, can have better insulating resistance properties than the inorganic pigment. The organic pigment, however, but may need to be included in a larger amount than the inorganic pigment in a photosensitive resin composition to accomplish equivalent light shielding properties, which can possibly deteriorate pattern developability and can produce a residue.